This invention relates to a method of and apparatus for cutting narrow grooves either part way or completely through a workpiece by electrolytically removing material from the workpiece.
It has previously been suggested that a groove could be electrolytically cut in a workpiece by using a rotating imperforate disk as an electrode in the manner disclosed in U.S. Pat. No. 3,130,138. As the rotating electrode disk approaches the workpiece, electrical current flows between the workpiece and the electrode disk. The patent states that using an electrode disk to form a groove results in undesirable electrolytic action between the sides of the disk and the groove with a resulting widening of the groove.
The aforementioned U.S. Pat. No. 3,130,138 indicates that solution of the problem of excessive widening of the groove has previously been attempted by providing an electrically insulating coating on the sides of the rotating disk to prevent electrolytic action between the major sides of the disk and the groove. However, these efforts were not satisfactory and improved results in thinness of cuts could be obtained by rotating electrode disks at speeds above 3,000 feet per minute. The patent indicates that the resulting groove will have a width which is about 0.02 inches greater than the thickness of the electrode disk, that is, there will be approximately 0.01 inches of space between each side of the electrode disk and a side surface of the groove. The patent also indicates that an electrode disk as thin as 0.036 of an inch has been used. According to the patent, a disk of this thickness would result in the formation of a groove having a width of approximately 0.056 inches.
Although the apparatus disclosed in the aforementioned patent may be generally satisfactory for some purposes, the apparatus cannot be used to form relatively narrow grooves, that is grooves having a width of 0.011 inch or less. Therefore, other method and apparatus have to be used when relatively thin grooves are to be formed.